The present invention relates to a semiconductor device and a power amplifier using the same.
In recent years, with the rapid growth in demand for mobile communication equipment, research and development of compound semiconductor devices for power amplifiers used in mobile communication equipment has been actively conducted. As one of such compound semiconductor devices, a hetero junction bipolar transistor (hereinafter called xe2x80x9cHBTxe2x80x9d) which has a high current drivability has been used.
AlGaAs has been widely used as a material for HBT emitter layers. However, there is an increasing trend to develop HBTs which use InGaP instead of AlGaAs because the former is more reliable in use over a long period that the latter. An example of an HBT which uses an InGaP emitter layer has been disclosed, for example, in Japanese Patent Laid-Open Publication No. 07-106343.
This prior art is illustrated in FIG. 15. An n-type GaAs emitter protective layer 306 is formed on an n-type InGaP emitter layer 305; an SiO2 side wall 313 is formed on the area of the n-type GaAs emitter protective layer 306 which corresponds to the guard ring 312 of the n-type InGaP emitter layer 305. The n-type GaAs emitter protective layer 306 prevents direct contact between the n-type InGaP emitter layer 305 and the SiO2 side wall 313, thereby avoiding an increase in a leakage current.
The present invention has an object to provide a semiconductor device in which, in a bipolar transistor having an emitter layer consisting of a semiconductor containing indium, a GaAs emitter protective layer is not used as a protective layer for preventing an increase in a leakage current between the emitter and base, and also provide a power amplifier using the same.
The above-said object can be achieved by covering the emitter layer guard ring surface of the bipolar transistor having an emitter layer consisting of a semiconductor containing indium, with a protective insulating film which contains silicon (Si) and oxygen (O) and has a density of oxygen of less than 7xc3x971022 cmxe2x88x923.
It is also acceptable that the density of oxygen of the protective insulating film is 3xc3x971022 cmxe2x88x923 is or less, or 8xc3x971021 cmxe2x88x923 or less.
Also, the protective insulating film may further contain nitrogen (N) or hydrogen (H) as well.